In case you are not familiar with it, the idiom It’s no use flogging a dead horse means that the outcome is already decided and no further effort can change that outcome.
It means, furthermore, that it is blindingly obvious that to continue expending effort is a waste of time.
I read somewhere, and I think it was either in a Philip Dick science fiction novel or one of Oliver Sacks’ books, that people suffering from schizophrenia have difficulty in seeing the illustrative side of idioms.
A schizophrenic would therefore tend to see the situation literally, with someone flogging a dead horse.
What a terrible situation to be in – to fail to see the meaning and therefore lead oneself down a path far from what the other is talking about.
Oliver Wolf Sacks was a British neurologist, naturalist, historian of science, and author.
In Awakenings, published 1973, he wrote about people who had encephalitis lethargica and were in a kind of suspended animation, in some sense disconnected from the outside world and yet able to interact with it in limited ways.
He explained a novel treatment for patients who had been victims of the 1920s encephalitis lethargica epidemic.
The National Institute of Health in the USA describes the disease this way:
Encephalitis lethargica is a disease characterized by high fever, headache, double vision, delayed physical and mental response, and lethargy. In acute cases, patients may enter coma. Patients may also experience abnormal eye movements, upper body weakness, muscular pains, tremors, neck rigidity, and behavioral changes including psychosis. The cause of encephalitis lethargica is unknown. Between 1917 to 1928, an epidemic of encephalitis lethargica spread throughout the world, but no recurrence of the epidemic has since been reported. Postencephalitic Parkinson’s disease may develop after a bout of encephalitis-sometimes as long as a year after the illness.
It was by noting some similarities to Parkinson’s disease that Sacks intuited that treating patients with L-DOPA might alleviate their symptoms.
In the book, and in the film that followed, the patients are described as awakening by the treatment using the then-new drug L-DOPA but then heartbreakingly – falling back into the same lethargic state bordering on coma that they had endured for decades before being treated with the drug.
However, in 1982 Sacks wrote:
I have become much more optimistic than I was when I wrote Awakenings, for there has been a significant number of patients who, following the vicissitudes of their first years on L-DOPA, came to do – and still do – extremely well.
Such patients have undergone an enduring awakening, and enjoy possibilities of life which had been impossible, unthinkable, before the coming of L-DOPA.